The invention relates to fittings used for brazing and soldering of tubes.
Various techniques for brazing and soldering tubes are conventional and known. In one such technique, the tubes are first cut square and the burr is removed. Pipe ends are mechanically cleaned until the oxides are removed, and then a flux paste is applied with a small brush or a clean cloth. The parts are pushed into the fitting and the surplus paste should be wiped off. The joint is then heated. As soon as the soldering temperature is reached, additional solder is added by hand until the capillary space is filled.
Usually, the plumber cuts the tubes, assembles the pipe with the fittings and attaches the system to a wall until the entire network of pipes is complete. Before soldering, the pipes must be removed and put into pieces in order to enable the addition of the flux.
The fluxes are corrosive, therefore, they should not come into direct contact with the human body.
To prevent the fluxes from fast settling and to adjust the viscosity of the fluxes, organic substances are added. However, the use of these organic additives during the soldering process has many disadvantages. The additives burn, have a disagreeable odor, produce carbon black, and cause pores in the soldering seam. These disadvantages are especially evident when the solders ar overheated. It is very difficult for even an experienced plumber to determine when the proper soldering temperature is reached.
An improvement can be realized if a solder powder is added to the flux. By watching the flux carefully during the heating process, the user can realize when the solder powder melts. That gives him an indication that the optimal soldering temperature is close. The amount of solder powder present in such pastes is too small to completely fill the capillary space; therefore, it is necessary for the user to feed additional solder by hand. Penetration of the solder around the joint must be visually observed, and a fillet should form between the pipe and the fitting.
Flux residues are corrosive. They must be completely removed by rinsing the tubes with water. Fluxes with organic additives have created a great corrosion problem. Organic components which were not completely soluble in water, incorporated halogen containing flux residues. These covered flux residues have caused severe pitting corrosion in the copper tubes.
When adding solder by hand, it is not possible to exactly measure the amount added. Normally, the operator uses much surplus solder, which ca then penetrate into the tube and block it.
If the tubes are laid into a wall, it is not possible to add the solder from the back. It is this situation which is often the reason for an incomplete filling of the capillary space. This results in leaky fittings.